Method for purifying acetylene gas and manufacturing acetaldehyde therewith



Dec. vl2, 1939. E. v. M .IRFu-nalalz- Y2,183,148 METHOD FOR PURIFYING AETYLENE G'AS AND MANUFACTURING ACETALDEHYDEA. TI'IEREWI'LH,

Filed Nov. 25,` 1/931 wilg mzwmmh a. Nw A,

'Patented Dec. 12, 1939 UNITED STATES PATENT 4orrlcia METHOD FOR PURIF'YING ACETYLEN GAS f AND MANUFACTURING ACETALDEH'YDE THEREWITH Eger V. Murphree, Baton Rouge, La., as signor to Standard Oil Development Company, a oorporation o! Delaware Application November 25, 1931, Serial No. 577,285

15,01aims.

usual source of the latter has been calcium car-- bide, yielding acetylene gas ln concentrated form.`

The process described herein makes available an abundant and cheap source of material for organicsynthesis. y

In accordance with this invention, the dilute gas used may vary in acetylene content between about 6% and 30% This is prepared by any suitable arc process, various forms of which have lbeen knownior many years. The preferred source of gas for ,the arc process is an olen-containing hydrocarbon, as will be" described. I have 2o found that the gases resulting fromthis type of process are suitable for the manufacture of acetaldehyde and the like, but that they contain impurities which mustv be removed before the acetaldehyde reaction takes place. Otherwise the impaired or ruined. Among these impurities are diacetylene and othercompounds which I have found to be removable by solution in oil'and other solvents. It will be understood that other processes (e. g. catalytic cracking) for making dilute acetylene gas may be substituted for the arc, if

they yield gases capable of being puried as herein described. Reference is to be made to the accompanying 35 drawing, in which the figure is a side elevation of preferred equipment for carrying out the process. In the drawing, reference numeral i denotes an arc oven for the conversion of natural gas, coke Y oven gas, cracked gases from oil reneries or similar material into acetylene. The gas is supplied through line 2.v The construction and operation of the arc form no part of the present invention. The gases from the arc, containing usually between and 25% of acetylene, are passed through a pipe 3 into a cooler 4 preferably in the form of a packed column. Water may be flowed downward through the tower from pipe 5 and discharged through pipe 6. The cooling is obtained by water of the usual feed water temperature.

The cooled gas, at atmospheric or somewhat higher pressure, passes throughv pipe 1 into a gas holder 8. From this it owsby pipe 9 into a compressor l Il which receives also recycled gas from a source to be described later. The compressor may 5 be bypassed if desired through a line l I controlled catalyst (metallic oxides, etc.) would be quickly (Cl. BSO-605) by valves lla and lib. In the normal operation of the process the gas ows through the compressor and is raised to a pressure of about to 40 pounds per square inch, at which pressure it flows through a cooler i2, which reduces it to atmospheric temperature or thereabout, and thence through pipe i 3 into the diacetylene scrubl ber l. This is preferably a tower with baiiles or other means to bring the gas into good contact with the scrubbing liquid which is introduced at 10.

the top through pipe i5. l

The scrubbed gas passes through line lli, into Awhich steam is also introduced through line ita, into heat exchanger il and thence through line it into the catalyst chamber is for the conversion of the puried acetylene to acetaldehyde.- The catalyst chamber is charged with any suitable form of catalyst such as metallic oxides. Any known or desirable way of converting the acety iene to acetaldehyde may be employed as this does not form in itself a part of the present invention. In line iii there is inserted a bypass 2@ controlled by valves 2i and'EZ. This bypass connects with a heater 23 which can be adjusted to bring the gas to the exact temperature required in the catalyst chamber when starting the equipment.

The gas from catalyst chamber i9, containing acetaldehyde equivalent to most of the acetylene entering the catalyst chamber,'pass es through a line 2d and heat exchanger il, thence through line 25 into the cooler 2t. This is a tubular apparatus using water as the cooling medium. The product from the cooler is either taken directly through line 28 to weak acetaldehyde storage tank 2@ or is passed through line 30 into the lower part oi a wash tower 3i.

In the Wash tower 3i the acetaldehyde-containing gas is brought into contact with water which iiows in through pipe 32. The tower has the usual Abaille plates, packing or the like. The amount of water is controlled so as to adequately dissolve the acetaldehyde without unduly diluting v the product. The solution of acetaldehyde in water, together with any other liquid products formed in the reaction, passes through line 28a 45 and line 28 from the bottom of tower 3l into the storage tank 29. From this tank a pump 83 orwards the liquid via line 34 through heat exchanger 35 and pipe 34a into the upper part of tower still 36. Heat exchanger 35 may be bypassedthrough line 31. Flow through this line and line 34 is controlled by valves 38 and 39 respectively.

is heated at'the bottomv by closed Steam coil 40 or other suitable heating means, 55

ile

The still such as direct steam, and bell cap plates or the like are provided throughout the greater part o1' the height of the tower. The product collecting in the bottom is withdrawn through line 4I and tlows in heat exchange with the acetaldehyde liquor passing through exchanger 35. 'I'he vapor coming of! at the top of the tower still through line 42 is concentrated acetaldehyde. The mixture passes through the condenser coil 43 into reflux tank 44. A part of the liquid in this tank is sent by pump 45 to the upper part of tower 36 through line 46 to serve as reux therein. The bulk of the product entering tank 44 runs through line 41 into the concentrated acetaldehyde storage tank 48. From this it may be withdrawn as desired through line 49 for conversion into acetic acid or other products.

Any gases uncondensed in coil 43 are separated in tank 44 and passed through line 50 into the vent line 5I. Also any gases that may be liberated in tank d8 pass through line 52 into the vent line. This leads to a suitable washer 53 and thence through line 56 to gas holder 8 for reuse in the process.

In the foregoing the passage of the acetylene and its products has been described. Reference will now be made to the means for purifying'the acetylene.

As indicated above the primary purification is obtained in the diacetylene scrubber I4 which receives a solvent liquid through line I5. This line is supplied from a tank 55. It is preferably charged with a hydrocarbon oil such as gas oil, or other solvents of diacetylene and impurities in the gas may be employed, for example, ace.-

tone, toluene, etc.

The oil charged with impurities is passed from the bottom of tower I4 through line 56 into the top of the acetylene stripper 51. In the form of equipment illustrated this is a compartment at the top of a tall tower 58 which serves for stripping out the diacetylene from the solvent oil. It will be understood, however, that separate towers or a plurality of separate towers may be used.

The pressure in acetylene stripper 51 is somewhat Alower than in scrubber I4. The pressure sure to about 3 pounds per square lnch gauge.

' The greater part of the acetylene dissolved in the solvent oil is removed by passing through the oil a countercurrent stream of gas from the wash tower BI. This gas flows through line 60 and enters stripper 51 just above the partition plate I which separates it from the lower tower section 58. The acetylene removed from the oil together with the spent gas ilows through line 52 into compressor III. Recycled gas may also enter yat this point through line 54 connected as described with washer 53.

A'I'he oil freed from most of the acetylene but still containing diacetylene and other impurities passes through line 63 into the upper part of the lower section 58. The pressure in this section is about the same as in section 51, but if desired a diil'erentlal pressure may be established using the control valves 58 and 59'. The impure oil flows down over the plates in section 58, meeting as it does so an ascending current of Aspent gas which is introduced via line 60 and branch line 54. A part of this spent gas maybe diverted through line 65 to the gas holder 66. Valves 51 and 68 control ilow through lines 64 and 50 respectively. The oil discharged from the ybottom of tower 58 through line 1I) is substantially pure and can be recycled directly to tower I4.

The gas from holder 66 is passed through line 1I into compressor 12 which forwards it either through line 13 to burners or for other use or `through line 14 to the arc furnace I. Valves 15 and 16 control ow through lines 13 and 14 respectively.

It will be observed that in the process described there is a direct passage from natural or crackedgas to acetaldehyde without any concentration of the acetylene. This greatly simplifies the process. It is further simplified by the use f the spent gas from the acetaldehyde wash tower to remove the acetylene and the impurities from the charged solvent oil. This gas comes from the high pressure scrubber I4 and is therefore under suillcient pressure to flow countercurrent to the oil in both sections 51 and 58. It is not intended to limit the invention to the use of this spent gas as the stripping agent as obviously other inert gases could be used. However, it is preferable to operate as described.

I have found that the impurities are removed by countercurrent flow of solvent oil or other solvent with the dilute acetylene gas. Heretofore various chemical means have been adopted to purify acetylene for conversion into acetaldehyde. The solvent oil may be used repeatedly after revivifying it as described. The two-stage removal of acetylene and diacetylene permits the recovery of the former for reuse in the process.

The Isystem may be iiushed out by introducing nitrogen or other suitable gas through line 1Ia. Flushing gas may be introduced also through line 11 and pump 18.

'Ihe following example is illustrative of a preferred method of operating: A gas obtained from the high pressure cracking of petroleum oil and containing or more of oleilns is passed through line l into the arc furnace I. It is there converted into a mixture containing between and 25% of acetylene associated with some diacetylene and other impurities. These are absorbedl in scrubbing tower I4 operated at a pressure of -40 pounds per square inch and at atmospheric temperature. The puried acetylene is passed through line I6 to the catalyst chamber I9 and is thereafter treated as described for the preparation of acetaldehyde.

The solvent oil is stripped in section 51 by means of spent gas under a slight pressure and at atmospheric temperature for the removal of acetylene. A small part of the diacetylene may be removed simultaneously but this will do no harm in the recycling through the operation.

The oil containing the bulk of the diacetylene is freed from it by stripping with the spent gas in section 58 at a slight pressure and at atmospheric temperature. The purified oil is returned to scrubber I4 and the removed diacetylene and gases associated with it are disposed of as described. There is no objection to passing a certain amount vof diacetylene through the arc furnace as it may in part be converted into acetylene, so that this does not result in building up a quantity of diacetylene in the circulating system. In any case it finally leaves the system through line 13 which prevents any serious increase in concentration.

Although the invention has been described as intended for the direct conversion of acetylene into acetaldehyde, it will be understood that the preliminary stages of purification are equally applicable if the acetylene is to be used for other chemical reactions. The puried acetylene may 15. Process of purifying gases containing a substantial amount of acetylene and some impurities of the nature of diacetylene, which comprises contacting said gases with gas oil as a solvent for said impurities, at a superatmospheric pressure between the approximate limits of 20 to 40 lbs. per sq. in. and at about atmospheric temperature, thereby eecting removal of at least a major proportion of the impurities 'out not more than a minor proportion of the acetylene.

EGER V. EmEHE-EE. 

